[mechanickeith]

Here are 4, 4 bolt pumps. For everyones info, 2 of these pumps are correct for the 4 cyl Tempest. One is correct for an early Pontiac V8 & one isn't worth the stamped steel it is made out of.

Notice that all 4 have the same casting number on them.

Looking at the impellers you will see the one that is stamped steel. This was purchased at NAPA & is incorrect for the 4 cyl's & V8's!!! The impeller is not the correct diamater or depth & will cavitate/bypass coolant & your motor will run HOT!!!


Next, look at the thickness of the impellers. You will see one that has much taller vanes & is sitting close to the pump housing. This is correct for a early V8.

Now for the Tempest 4 cylinder pumps!! Notice that 2 pumps have a shallow vane impeller & the impeller is off of the pump housing by about a 1/2 inch. This IS correct for our 4 cylinders. This different impeller sits further back in the timing gear/pump housing & only pumps the water that is in the back half of the housing. The back half of the housing is the half that supplies water to the right bank of cylinders. Our little 4 cyl motors use the same timing housing that is used on the V8's but the water pump impeller was modified so it only pumps water to the right half.

You can run a V8 pump in the 4 cyl & it will pump coolant & cool, but,,,, The motor is just wasting energy trying to pump coolant to a half of a motor that is not there. So, next time you have your water pump out, check the impeller!!!!!!!

Last but not least!!!! I have yet to be able to purchase a correct 4 cylinder new/rebuilt 4 bolt water pump from ANY parts house/supplier!!! What I have been doing is purchasing a V8 pump from NAPA, pressing the pumps apart & putting the correct impeller on the new pump!!!

http://www.kodakgallery.com/ShareLan...localeid=en_US

Keith

PS!!! The correct pumps are the first & 3rd!!

[TempestFugit]

VERY Helpful information. Thanks for Posting it.

[Scott M]

Try contacting Cardone in Philly; they're a rebuilder.

[mechanickeith]

Hi Scott, I spoke with Cardone late last year. The only Pontiac 4 bolt pump they will do is the 55's- early 60's. They said there is not enough demand to do a correct Tempest 4bolt pump with a cast impeller.

Keith

[hootsk]

Too awesome, Keith. We need one of these from an expert for every part!

Chuck

[mechanickeith]

Got another one coming!!!

[Peter Serio]

Hi Keith, that was a GREAT post I've got several 4 bolt water pumps out in the garage & always wondered what the variations were!!!

I knew there was something different about them.

[mechanickeith]

Check them out guy!! I bet at least a couple are wrong for the Tempest!! I have several more pumps somewhere. One has a cast impeller that is set up for the 4 cyl but the vanes look quite different!! Will see if I can find it & post a pic.

If anyone needs a water pump & cant find one, & your old pump has the correct impeller, I can do the press work to transfer the impeller to a rebuilt pump.

Keith

[Peter Serio]

I have at least one old water pump here that has a cast iron impeller and the fins radiate outwards in a spiral pattern beginning at almost the very center of the hub.

[mechanickeith]

That is the one I was talking about!! I have one somewhere. It is a 4 cyl pump because the impeller is shallow & set to the rear of the timing gear housing. Can you post a pic of it??

[Peter Serio]

Here it is:

[mechanickeith]

Yep!!! Just like one I have. I dont know the reason for the different impellet. Let me dig back in my books & see if I can find a reference to it. Maybe for heavy duty applications like Taxi or cop car??

[Peter Serio]

I've got 4 of 5 of these old 4 bolt timing cover pumps here, they are all different from one another in some way. I wonder why they made so many variations for just a simple pump?

So the general theory is the old cast impellers are what you want to run?

[mechanickeith]

Yes!! The cast impeller is designed to fit the opening in the timing gear housing. You want the shallow vane impeller that has a 1/2 inch gap between the impeller & the pump housing. This shallow vane impeller fits the rear cavity only. The V8 impeller fits the opening but it try's to pump water to the left side also. Waste of power. I found several pictures in some of my ASE books from 1960 that shows a cutaway of the gear housing & the pump. Is clearly shows the impeller in the rear gear housing cavity. I dont have a scanner or I would post some pics. Maybe my camera can get a clear pic?? will give it a try.

OK, I'm back!! Pics should be here http://www.kodakgallery.com/ShareLan...localeid=en_US I took 3 pics of the ase book page, 2 are closeups of the pump impellers as thay sit in the gear housing. You can see the 4 cyl pump only pumps coolant in the back half of the housing. Note how the impeller fits the opening & the round rear part of the impeller seals off the front & rear sections. The second pic is of the V8 pump, the 3rd pic shows the Tempest 4 cyl pump.

[hootsk]

Keith this is invaluable. I went out the shop and pulled the crate of 63 326 parts because I thought I remembered seeing one of these. Sure enough, someone had installed one of the 4 cyl pumps in the V8. Maybe that was part of the reason it died!

Chuck

[Peter Serio]

Mid-way thru the 1963 Model year they changed the timing gear cover casting to take the "new" 8 bolt water pump. Are there 4 cyl & V8 versions of the 8 bolt water pump as well?

[mechanickeith]

If you have a Factory 63 tech manual, go to page 6A-2 There are pics of the 2 different 4 bolt water pumps. I know it was mid year 63 that they went to the 8 bolt cover. I dont doubpt that the pumps got swapped around & caused all sorts of over heat problems, especially for the V8's!!!

[mechanickeith]

Peter, I have never seen an 8 bolt pump on a 4 cyl. Not saying it never happened, just have not seen it.

[63Banshee]

I've got a 1 or 2 4 cyl 8 bolt pumps. I'll post pictures when I can get to it.

[John V.]

Peter, to answer your question, yes there were 4 ctl & V8 versions of the 8 bolt pump.

The '63 4 cyl pump used the same body casting as the '63-'65 V8 pump.

Couple years ago somebody here (I'd have to dig up the file to remember who) had an NOS '63 8 bolt 4 cyl pump (identified by SR p/n). We did some research to identify the differences between it and the 8 cyl version (taller vanes IIRC on the V8 version).

They both used the same pump body casting (as cast on the body) but the assembly p/n under which they were serviced was different (as listed in the MPC).

Pontiac of course presumably kept them straight at the factory but no telling what a rebuilder would have done when rebuilding the cores.